Method of stabilizing the color of the disodium salt of 5,5'-indigotin disulfonic acid

Abstract

The color of the disodium salt of 5,5'-indigotin disulfonic acid (i.e., FD&C Blue No. 2) in aqueous media held in an aluminum container is stabilized by the addition of tannic acids, ortho-phenanthroline, apoferritin.

Having then described the invention what is claimed is: 
     
       1. A method for stabilizing the blue color of a disodium salt of 5,5'-indigotin disulfonic acid in an aqueous fruit-flavored dessert gel having a pH of less than 4.5 and which is contained in an aluminum container by adding to said gel an amount of a complexing agent selected from the group consisting of tannic acids, ortho-phenanthroline, apoferritin and combinations thereof, said complexing agent being added at a weight level of from 0.5-5.0 times the level of the disodium salt of 5,5'-indigotin disulfonic acid, the level of the complexing agent being below its taste threshold level in the gel. 
     
     
       2. The method of claim 1 wherein the complexing agent is a tannic acid and the level is from 0.5 to 3.0 times the level of 5,5'-indigotin disulfonic acid. 
     
     
       3. The method of claim 1 wherein the complexing agent is ortho-phenanthroline and the level is from 1.0-5.0 times the level of 5,5'-indigotin disulfonic acid. 
     
     
       4. The method of claim 1 wherein the complexing agent is apoferritin and the level is from 1.0-5.0 times the level of 5,5'-indigotin disulfonic acid. 
     
     
       5. The method of claim 1 wherein the gel contains a gelling agent selected from the group consisting of gelatin, carrageenan, algin, agar and combinations thereof. 
     
     
       6. The method of claim 1 wherein the gelling agent is gelatin. 
     
     
       7. The method of claim 1 wherein the gel also contains FD&C Red No. 40 at a level effective to produce a purple color in the gel.